1. Field of the Invention
This invention relates to an apparatus and method for dilating occluded or stenotic blood vessels and more particularly to such an apparatus and method which include inflating a dilating balloon carried by a catheter to widen a passage through a stenosis, and trapping fragments of plaque broken off by dilation in a filter which collapses in a manner which retains the fragments while the catheter is removed from the blood vessel.
2. Background Information
It is becoming common practice today to open occluded (i.e. blocked) or stenotic (i.e. narrowed) blood vessels by inserting a catheter carrying a toroidal balloon into the vessel and inflating the balloon to press the stenosis radially outward against the wall of the blood vessel. While this is often effective in increasing blood flow through the vessel, embolic fragments of the stenosis can break loose and be carried by the flow to other parts of the circulatory system where they can lodge and cause a blockage. It is also important in such a procedure that the interruption of blood flow through the vessel be minimized. This is especially important in thecase of the carotid artery carrying blood to the brain of a human.
It is a primary purpose of the present invention to provide a catheter for dilating an occluded or stenotic blood vessel which includes, in addition to a dilating balloon, a filter device for trapping embolic fragments of the stenosis dislodged by dilation.
It is another important object of the invention to provide such a filter device carried by the catheter which is insertable into the occluded or stenotic vessel in a retracted position, and can be easily and reliably remotely extended.
It is yet another object of the invention to provide such a catheter with a filter which securely retains embolic fragments of the stenosis when the filter is retracted for removal from the blood vessel.
It is still another object of the invention to provide such a catheter with an extendable and retractable filter which minimizes trauma as the catheter is inserted and withdrawn from the blood vessel.
It is also an important object of the invention to provide a method of dilating occluded or stenotic blood vessels which includes mechanically trappng embolic fragments of the stenosis dislodged by dilation and removing them from the vessel without spillage.
It is a further object of the invention to achieve the previous objects with minimum interruption of blood flow through the vessel.